The same or similar Israel-aligned groups and donors have spent hundreds of millions of dollars in recent decades, and that money poured into American politics through a variety of channels, according to the non-profit, non-partisan Center for Responsive Politics. The CRP uses federal election records to track campaign finance spending and makes its data available on the OpenSecrets site.

The Guardian examined campaign finance data after Muslim Minnesota congresswoman Ilhan Omar ignited a controversy with two tweets claiming pro-Israel lobby money influenced American political policy and discourse. The claim led to broad accusations of antisemitism from Democrats and Republicans. Omar later apologized but also stood her ground when it came to highlighting the influence of lobbyists, comparing influential pro-Israel lobby group, the American Israeli Public Affairs Committee (Aipac) to the the National Rifle Association and the fossil fuel industry.

The data examined by the Guardian suggests that the pro-Israel lobby is highly active and spends heavily to influence US policy, though at levels far below those of many big business sectors.

“I haven’t observed many other countries that have a comparable level of activity, at least in domestic lobbying data,” said Dan Auble, a senior researcher at CRP.

Omar incorrectly suggested Aipac makes campaign contributions to candidates. However, records show it did spend about $3.5m lobbying during the 2018 election cycle. In total, pro-Israel lobbying groups spent about $5m in 2018, the highest tally since tracking began in 1998.

Aipac spent the most of the lobbying groups, and is known for funding junket trips to Israel for freshman lawmakers and senators, as well as state legislators. Aipac also lobbied against the Iran nuclear deal in 2015 and supported the Trump administration’s withdrawal from the agreement.

An Aipac spokesperson did not return requests for comment.

Separately, pro-Israeli foreign agents registered under the Foreign Agents Registration Act, which can include lobbyists working on behalf of the Israeli government, companies, political parties and other organizations spent about $46.3m in 2017 and 2018, behind only Japan and South Korea. However, only about $2.1m of that total funded political activity, while $44.2m was dedicated to tourism and other industries.

Pro-Israel groups and individuals also contributed just under $15m to US politicians’ campaigns during the 2018 cycle, the highest amount since the 1990 cycle. The J Street Pac, a progressive, pro-Israel lobby that advocates for a two-state solution to the Israeli-Palestinian conflict, contributed the most at $4.03m. The nonpartisan NorPAC contributed $1.1m, while the Republican Jewish Coalition contributed about $502,000.

J Street senior political adviser Ben Shnider didn’t comment specifically on what the lobby gets in return for its investment, but said the high level of contributions to his lobby indicates support for a “diplomacy first Middle East policy”.

“What that demonstrates is that there’s momentum behind a pragmatic, pro-diplomacy, moderate approach to the Middle East, and to the Israel-Palestine issue,” he said.

Democratic leaders who criticized Omar and demanded an apology also receive a high level of contributions from the pro-Israel lobby. Eliot Engel, chair of the House Foreign Affairs Committee on which Omar sits, received $1.07m from the pro-Israel lobby during his career, more than he’s received from any other industry. In a Tuesday statement, he said “… it’s shocking to hear a Member of Congress invoke the anti-Semitic trope of ‘Jewish money.’”

It’s also highly likely that there’s far more pro-Israel lobby money flowing into American politics than is tracked. Dark money nonprofits aren’t required to disclose their donors, and OpenSecrets doesn’t fully track how mega-donors spend their cash. For example, Sheldon Adelson, the largest overall donor in 2018, gave $250,000 to the Republican Coalition Jewish Victory Fund, but that donation isn’t factored into any of OpenSecrets’ other contribution and lobbying tallies.

At this spending level, the pro-Israel lobby is far more active than PACs aligned with other nations. The US-Cuba Democracy Pac’s approximately $171,000 in campaign contributions in 2018 was the most among foreign policy Pacs that aren’t aligned with Israel. Still, the pro-Israel lobby spends relatively little compared to other industries – the securities and investment lobby contributed $389m in the 2018 cycle alone while the real estate industry spent $186m.

It is that level of spending by industry and corporate donors and lobbyists – and its likely influence on American politics – that is the “overarching, systemic concern” when it comes to campaign finance, and comments like those by Omar, said Brendan Fischer, director of the federal reform program at the Campaign Legal Center.

“The US political system is very dependent on money, and in a political system less reliant on money for electoral success, we wouldn’t have to be asking these questions,” he said.